JP3323345B2 - Magnetic circuit for speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic circuit for a speaker, and more particularly to a magnetic circuit for a speaker for reducing harmonic distortion.

[0002]

2. Description of the Related Art A magnetic circuit is an important component constituting a drive source of a speaker unit, but current speakers use many metal parts and have various problems.
Current loudspeakers as described in Japanese Utility Model Application Laid-Open No. 62-186596 have an iron serving as a yoke arranged close to the inner and outer diameters of the voice coil. In this case, the eddy current generated in the iron causes distortion of the speaker voice. It is also a cause of occurrence. When an iron part is used for the magnetic gap, it causes eddy current distortion due to the conductivity of iron, and it is difficult to form a free shape.
Since the shape is limited to a shape that can be designed by bending and drawing, the efficiency of the magnetic circuit is deteriorated.

[0003]

One example of a conventional magnetic circuit configuration of a speaker is as follows. As shown in FIG. 7 , a sintered ferrite magnet 74 having anisotropy in the axial direction (Y direction) is used, and iron members (yoke) 73 are provided above and below it.
The magnetic gap portion 79 is formed by arranging 77. In this conventional speaker, an iron member (yoke) is attached to the magnetic gap portion 79.
73 and 77 have the following disadvantages. 1) speaker operation, by passing the sound current (AC) to the voice coil 76, but is operated, and causes of magnetic field eddy current is generated in the iron member (yoke) 73 and 77 by the distortion of the voice coil 76 Has become. (The iron member is soft iron and conductive, and when an AC magnetic field crosses it, an eddy current is generated in a direction that hinders its change.) 2) The voice coil 76 itself has a very low inductance, When it is arranged close to the magnetic circuit (the inner and outer soft irons), the inductance becomes high, the impedance increases in the middle to high range, and the conversion efficiency decreases. At the same time, the phase rotation by the impedance Lucas also increases, causing phase distortion in the output signal. 3) Since the magnetic field generated by the magnet was converted only by the high magnetic permeability of iron, the conversion efficiency was poor and the leakage magnetic flux was large. An object of the present invention is to provide a lightweight and inexpensive speaker magnetic circuit while reducing distortion caused by the speaker magnetic circuit.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a conventional magnetic circuit for a loudspeaker, in which a peripheral portion between a ring-shaped ferrite core fixed to a frame and a ring-shaped magnet peripheral surface fixed to a frame is provided. The problem is to be solved by employing a technical means in which a magnetic gap is formed in the magnetic gap, and a voice coil interlocked with the diaphragm is arranged in the magnetic gap and driven in the axial direction.

[0005]

According to the present invention, the iron yoke forming the magnetic gap portion, which has been considered to be essential in the past, is eliminated, and a new magnetic circuit configuration is provided. Ferrite cores are lightweight and oxide M
Since nZn ferrite and NiZn ferrite are used , no eddy current is generated. Neodymium, iron,
By using a boron magnet or the like, a high magnetic flux density can be generated in the magnetic gap. By using a bonded magnet containing rare earth metal magnet powder as the ring-shaped magnet, eddy current generated in the magnet can also be prevented. By forming a magnetic gap between the peripheral surface of the ferrite core and the peripheral surface of the ring-shaped magnet, the leakage magnetic flux is small and the efficiency can be improved. The direction of the magnetic flux passing through the inside of the magnet can be freely formed by devising the magnetization. Thus the form of the frame to the molding of a resin such as
And a ring-shaped ferrite core or phosphorus
A ring-shaped magnet or a projection that holds the inner circumference of the
By providing a concave portion for holding the outer peripheral portion of the ring-shaped ferrite core , it is possible to accurately form a magnetic gap formed between the peripheral surface of the ring-shaped ferrite core and the peripheral surface of the ring-shaped magnet.

[0006]

The present invention will be described in more detail with reference to the following examples. Embodiment 1 FIG. 1 is a sectional view of a speaker incorporating the present invention. A
The convex portion 12 is formed on the bottom of the frame 11 made of a synthetic resin such as BS, and the inner peripheral portion 131 of the ring-shaped soft ferrite core 13 is bonded and fixed. Recess 114 of frame 11
The outer peripheral portion 141 of the bonded magnet 14 in which the NdFeB magnet powder is bonded with the resin is adhered and fixed at the inner peripheral portion. Bond magnet 1
4 and inner portions 142 and 143 and soft ferrite core 1
The magnetic gaps 152 and 153 are formed with the outer peripheral portion 132 of the coil 3.
2 and 163 are respectively disposed and coils 162 and 163
Are energized so that the driving directions are the same. The magnet 14 is subjected to NS magnetization as shown. Two voice coils are connected in series (series connection) or parallel connection (parallel connection)
In the case of series connection, if the winding direction of the voice coil is set to the opposite direction, the driving direction by energization becomes the same. In this case where the voice coil is connected in parallel, the inductance is further reduced to よ り compared with the case where the voice coil is connected in series, and the impedance can be reduced to higher frequencies. The output sound pressure characteristic, the impedance characteristic, the second harmonic distortion characteristic, and the third harmonic distortion characteristic of the speaker incorporating the magnetic circuit of the present embodiment and the speaker incorporating the conventional magnetic circuit shown in FIG. 7 were measured. These are shown in FIGS. 8 , 9 , 10 , and 11 , respectively. In these figures, the solid line (A) is for a conventional speaker, and the dotted line (B) is for a speaker utilizing the present invention. According to FIG. 8 , a speaker using the present invention has a small decrease in sound pressure level particularly in a high frequency band. In FIG. 9 , it is clear that the speaker using the present invention has less variation in impedance in the entire frequency band than the conventional speaker. Further, as shown in FIGS. 10 and 11 , in the loudspeaker using the present invention, both the second- order harmonic distortion and the third- order harmonic distortion are significantly reduced as compared with the related art. 12 and 13 show simulation results of magnetic flux leakage for a speaker magnetic circuit using the present invention and a conventional magnetic circuit, respectively. The magnetic circuit according to the present invention has a small leakage magnetic flux. According to the above embodiment, since the magnetic circuit is constituted by the soft ferrite core 13 and the bond magnet 14 which are non-conductive members, an eddy current is generated in the magnetic circuit by the AC magnetic field generated when the voice coils 162 and 163 are energized. Never do. Further, for example, when the speaker of this embodiment is embedded in a vehicle door, it is assumed that a ferromagnetic and highly conductive member such as an iron plate is disposed close to the outside of the speaker. The eddy current may be generated due to the AC magnetic fields of the voice coils 162 and 163, but the frame 11 covering the magnetic circuit portion is made of a non-magnetic material such as aluminum die cast, copper, or brass and has high conductivity. By forming from the material, the alternating magnetic field of the voice coils 162 and 163 is short-circuited in the frame 11 and is prevented from leaking from the frame 11 to the outside. Therefore, eddy current can be prevented from being generated in the magnetic circuit portion in the frame 11 and in the vicinity of the outside of the speaker, and the distortion of the audio signal can be reduced. Since the frame 11 is a non-magnetic material, the magnetic flux of the bond magnet 14 does not leak to the frame 11 and the magnetic flux density of the magnetic gaps 152 and 153 does not decrease. Embodiment 2 FIG. 2 is a sectional view of a speaker incorporating the present invention. A convex portion is formed at the bottom of the frame 21, and the inner peripheral portion of the ring-shaped soft ferrite core 23 is bonded and fixed. Frame 2
The outer peripheral portion of the bond magnets 246 and 248 in which the NdFeB magnet powder is bonded with a resin is adhered and fixed at the inner peripheral portion of the concave portion. The bond magnet 246 is bonded to the bond magnet 248 via a ring-shaped soft ferrite core 247. Magnetic gaps 252 and 253 are formed by the inner periphery of each of the bond magnets 246 and 248 and the outer periphery of the soft ferrite core 23, and the magnetic gaps 252 and 253 are formed.
53 are provided with coils 262 and 263, respectively, and are energized so that the driving directions of the coils 262 and 263 are the same. NS magnets are applied to the magnets 246 and 248 as shown in the figure, so that magnetic flux passes through the soft ferrite core 247. Note that a ring-shaped bond magnet may be provided instead of the soft ferrite core 247, and a ring-shaped soft ferrite core may be arranged above and below the bond magnet. In this example in which two voice coils are connected in parallel, the inductance is further reduced to 、, and the impedance can be reduced to a higher frequency. Embodiment 3 FIG. 3 is a sectional view of a speaker incorporating the present invention. A convex portion 312 is formed at the bottom of the frame 31 to form a ring-shaped N
The inner peripheral part of the dFeB magnet 34 is fixed. An outer peripheral portion of the ring-shaped soft ferrite core 33 is fixed to an inner peripheral portion of the concave portion of the frame 31. Two magnetic gaps are formed by the outer peripheral portion of the magnet 34 and the inner peripheral portion of the soft ferrite core 33, and coils 362 and 363 are arranged in these magnetic gaps so that the driving directions of the coils 362 and 363 are the same. Is energized. The magnet 34 is subjected to NS magnetization as shown. In this example in which two voice coils are connected in parallel, the inductance is further reduced to 、, and the impedance can be reduced to a higher frequency. FIG. 3 shows another embodiment of the present invention in which the ring-shaped NdFeB magnet and the ring-shaped soft ferrite core are interchanged. Embodiment 4 FIG. 4 is a sectional view of a speaker incorporating the present invention. A convex portion 42 is formed on the bottom of the frame 41, and the inner peripheral portion of the ring-shaped bonded magnet 44 is fixed. Recess 4 of frame 41
The outer peripheral portion of the ring-shaped soft ferrite core 43 is fixed at the inner peripheral portion of the ring. Magnetic gaps 452 and 4 are formed between the outer peripheral portion of the bonded magnet 44 and the inner peripheral portion of the soft ferrite core 43.
The coils 462 and 463 are respectively arranged in these magnetic gaps, and the coils 462 and 463 are energized so that the driving directions are the same. The magnet 44 is subjected to NS magnetization as shown. In this example in which two voice coils are connected in parallel, the inductance is further reduced to 、, and the impedance can be reduced to a higher frequency. Embodiment 5 FIG. 5 is a cross-sectional view of a speaker incorporating another embodiment of the present invention. A projection 52 is formed at the bottom of the frame 51,
The inner peripheral portion 531 of the ring-shaped soft ferrite core 53 is fixed. Outer peripheral portion 541 of bonded magnet 54 in which NdFeB magnet powder is bonded with glass at the inner peripheral portion of the concave portion of frame 51
Is fixed. A magnetic gap 552 is formed by the inner peripheral portion 542 of the bond magnet 54 and the outer peripheral portion of the soft ferrite core 53, and a coil 562 is wound around the bobbin 58 connected to the diaphragm in the magnetic gap 552. (Embodiment 6) FIG. 6 is a sectional view of a speaker incorporating another embodiment of the present invention . At the bottom of the frame 71 made of A Rumi die-casting to form a convex portion, it is bonded and fixed to the inner peripheral portion of the ring-shaped soft ferrite core 73. Two ring-shaped NdFeBs are provided on the outer peripheral side of the ring-shaped soft ferrite core 73.
The sintered magnets 746 and 748 are arranged. The two ring-shaped NdFeB sintered magnets 746 and 748 have outer peripheral surfaces, respectively.
(The outer circumferential surface opposite to the magnetic gaps 752 and 753) is adhesively fixed to and connected to the inner circumferential surface of the iron ring-shaped yoke 79. Then, the outer peripheral surface of the ring-shaped yoke 79 is fixed to the inner peripheral portion of the concave portion of the frame 71. Magnetic gaps 752, 7 are formed between the inner peripheral portion of each of the NdFeB sintered magnets 746, 748 and the outer peripheral portion of the ring-shaped soft ferrite core 73.
53 are formed, and coils 762 and 763 are disposed in the magnetic gaps 752 and 753, respectively.
Are energized so that the driving directions are the same. In this embodiment, an example in which an NdFeB-based sintered magnet is used as the ring-shaped magnet has been described, but a bond magnet in which NdFeB magnet powder is bonded with a resin may be used. Also, an example is shown in which two ring-shaped magnets are connected to the ring-shaped yoke, but two or more ring-shaped magnets may be used. In this embodiment, the frame is made of aluminum die-cast, but a synthetic resin such as ABS can be used.

[0007]

According to the present invention, the distortion caused by the magnetic circuit of the speaker can be reduced and the weight can be reduced extremely inexpensively.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment.

FIG. 2 is a longitudinal sectional view of a second embodiment.

FIG. 3 is a longitudinal sectional view of a third embodiment.

FIG. 4 is a longitudinal sectional view of a fourth embodiment.

FIG. 5 is a longitudinal sectional view of a fifth embodiment.

FIG. 6 is a longitudinal sectional view of a sixth embodiment.

FIG. 7 is a longitudinal sectional view of a conventional speaker.

FIG. 8 shows a conventional speaker and a speaker using the present invention.
FIG. 4 is a diagram showing output sound pressure characteristics.

FIG. 9 shows a conventional speaker and a speaker using the present invention.
FIG. 4 is a diagram showing impedance characteristics.

FIG. 10 shows a conventional speaker and a speaker using the present invention.
FIG. 3 is a diagram showing harmonic second-order distortion characteristics.

FIG. 11 shows a conventional speaker and a speaker using the present invention.
FIG. 4 is a diagram showing third harmonic distortion characteristics.

FIG. 12 shows a magnetic circuit for a speaker using the present invention .
Der those shown the simulation results of the leakage magnetic flux Te
You.

FIG. 13 shows the leakage magnetic flux of a conventional magnetic circuit for a speaker .
9 illustrates a simulation result.

[Description of Signs ] 11, 21, 31, 41 , 51 , 71 frames, 12 , 312 , 42 , 52 convex portions, 114 , 414 concave portions, 13 , 23 , 33, 43 , 53 , 73 soft blowjob
Core, 14,246,248,34,44,54,746,7
48 magnets, 152 , 153 , 252 , 253 , 452 , 453, 5
52,752,753 magnetic gap, 162,163,262,263,362,363,4
62,463,562,762,763 Voice Carp
Le, 247 soft ferrite core 79 York

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-155822 (JP, A) JP-A-58-50891 (JP, A) JP-A-59-80100 (JP, A) 80999 (JP, U) Actually open sho 57-109695 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 9/02 102 H04R 9/02 101 H04R 9/00

Claims (9)

(57) [Claims] A magnetic coil is formed between a peripheral surface of a ring-shaped ferrite core fixed to a frame and a peripheral surface of a ring-shaped magnet fixed to a frame, and a voice coil interlocked with a diaphragm is formed in the magnetic gap. A magnetic circuit for a speaker, which is arranged and driven in an axial direction. 2. The magnetic gap portion according to claim 1 , wherein:
Of both ends of the ferrite core in the axial direction and the ring-shaped magnet.
A pair is formed between both ends in the axial direction.
Voice coil linked to diaphragm in each cap section
The driving direction of each voice coil is the same.
The winding direction of these voice coils is specified so that
A magnetic circuit for a speaker according to claim 1 . 3. The ferrite core according to claim 1, wherein the ring-shaped magnet is a ferrite core.
And this ferrite core is joined to both axial ends.
The magnetic circuit for a speaker according to claim 2, comprising a pair of magnets . 4. The ring-shaped magnet includes a magnet and the magnet.
A pair of ferrite cores joined to both axial ends
The magnetic circuit for a speaker according to claim 2, comprising: 5. The ring-shaped magnet includes a magnetic gap portion.
And a pair of magnets facing the
It consists of a yoke material bonded to the opposite peripheral surface
A magnetic circuit for a speaker according to claim 2 . 6. The magnetic gap according to claim 1 , wherein
Between the outer periphery of the light core and the inner periphery of the ring-shaped magnet
And at the bottom of the frame, the ring
And a ring for holding an inner peripheral portion of the ferrite core and the ring
And a recess for holding the outer periphery of the magnet.
Item 3. A magnetic circuit for a speaker according to item 1 or 2 . 7. The ring-shaped magnet according to claim 7 , wherein:
Between the outer circumference of the ring and the inner circumference of the ring-shaped ferrite core.
And at the bottom of the frame, the ring
A convex portion for holding the inner peripheral portion of the ring-shaped magnet and the ring-shaped ferrite
And a recess for holding the outer periphery of the core.
Item 3. A magnetic circuit for a speaker according to item 1 or 2 . 8. The ring-shaped magnet is made of rare earth metal magnet powder.
The magnetic circuit for a loudspeaker according to claim 1 or 2, which is a bonded magnet containing powder . 9. The frame is made of a non-magnetic material and a conductive material.
The frame is made of
And the ring-shaped ferrite core is covered.
A magnetic circuit for a speaker according to claim 1 or 2 .